10% of Damage is taken from Mana before Life
Transfiguration of Mind 
Divine Guidance is a notable Ascendancy passive skill for the Hierophant that grants increased maximum mana and causes the character's mana to absorb a portion of the damage dealt to life. It also grants you "Transfiguration of Mind", causing increases and reduction to maximum mana to also apply to damage at 30% of their value.
As with other "Mana taken before Life" effects, this skill will deduct 10% of the damage that would be inflicted on the character's life is deducted from mana instead. If the character has insufficient mana, then the remainder of the damage will be taken from life. Damage dealt to energy shields will not be deducted from mana.
See Mind Over Matter for more details on the mechanic.